In an existing system for managing individual articles, RFID (Radio Frequency Identification) tags (also referred to as wireless tags) are attached to articles such as commodities, books, parts, or other materials. Information such as an identification number (ID) is recorded in a RFID tag attached to the article and is read by a RFID tag reader. In a library or the like, a large number of books with RFID tags may be densely arranged on shelves over a wide area. In a conventional wireless tag reading system, a mobile body provided with tag readers moves around in the area to read the RFID tags of the books for inventorying purposes. However, in the conventional wireless tag reading system, it is difficult to read each RFID tag at a high speed when a large number of RFID tags are densely positioned, as in a library.